
package org.apache.solr.internal.csv;

import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;

/**
 * Utility methods for dealing with CSV files
 */
public class CSVUtils {

    private static final String[] EMPTY_STRING_ARRAY = new String[0];
    private static final String[][] EMPTY_DOUBLE_STRING_ARRAY = new String[0][0];

    /**
     * <p><code>CSVUtils</code> instances should NOT be constructed in standard
     * programming.
     *
     * <p>This constructor is public to permit tools that require a JavaBean
     * instance to operate.</p>
     */
    public CSVUtils() {
    }

    /**
     * Converts an array of string values into a single CSV line. All
     * <code>null</code> values are converted to the string
     * <code>"null"</code>, all strings equal to
     * <code>"null"</code> will additionally get quotes around.
     *
     * @param values the value array
     * @return the CSV string, will be an empty string if the length of the
     * value array is 0
     */
    public static String printLine(String[] values, CSVStrategy strategy) {

        // set up a CSVUtils
        StringWriter stringWriter = new StringWriter();
        CSVPrinter csvPrinter = new CSVPrinter(stringWriter, strategy);

        // check for null values an "null" as strings and convert them
        // into the strings "null" and "\"null\""
        for(int i = 0; i < values.length; i++) {
            if(values[i] == null) {
                values[i] = "null";
            }
            else if(values[i].equals("null")) {
                values[i] = "\"null\"";
            }
        }

        // convert to CSV
        try {
            csvPrinter.println(values);
        }
        catch(IOException e) {
            // should not happen with StringWriter
        }
        // as the resulting string has \r\n at the end, we will trim that away
        return stringWriter.toString().trim();
    }

    // ======================================================
    //  static parsers
    // ======================================================
    /**
     * Parses the given String according to the default {@link CSVStrategy}.
     *
     * @param s CSV String to be parsed.
     * @return parsed String matrix (which is never null)
     * @throws IOException in case of error
     */
    public static String[][] parse(String s) throws IOException {

        if(s == null) {
            throw new IllegalArgumentException("Null argument not allowed.");
        }
        String[][] result = (new CSVParser(new StringReader(s))).getAllValues();
        if(result == null) {
            // since CSVStrategy ignores empty lines an empty array is returned
            // (i.e. not "result = new String[][] {{""}};")
            result = EMPTY_DOUBLE_STRING_ARRAY;
        }
        return result;
    }

    /**
     * Parses the first line only according to the default {@link CSVStrategy}.
     *
     * Parsing empty string will be handled as valid records containing zero
     * elements, so the following property holds: parseLine("").length == 0.
     *
     * @param s CSV String to be parsed.
     * @return parsed String vector (which is never null)
     * @throws IOException in case of error
     */
    public static String[] parseLine(String s) throws IOException {

        if(s == null) {
            throw new IllegalArgumentException("Null argument not allowed.");
        }
        // uh,jh: make sure that parseLine("").length == 0
        if(s.length() == 0) {
            return EMPTY_STRING_ARRAY;
        }
        return (new CSVParser(new StringReader(s))).getLine();
    }
}
